<!DOCTYPE html>
<html>
<head>
	<title></title>
	<script type="text/javascript">
	var sum=0;//班级总分
	var avg;//平均分
	for(var i=1;i<=3;i++){
		for(var k=1;k<=4;k++){
			while(k<=4){
				var num=Number(prompt('第'+i+'班'+'第'+k+'学生'+'成绩'));
				sum +=num;
				break;
			}
			avg=sum/4;
		}console.log(avg);
	}
	</script>
</head>
<body>

</body>
</html>